1. Field of the Invention
The present invention relates to a four-wheel steering system for an automotive vehicle, and more particularly to a four-wheel steering system in which lateral deviation of the vehicle is detected by detection of a front wheel steering angle and a yawrate or detection of lateral acceleration for determination of a desired steering angle of rear road wheels.
2. Discussion of the Prior Art
Disclosed in Japanese Patent Laid-open Publication 63-207772 is a four-wheel steering system wherein a front wheel steering angle, a yawrate and a vehicle speed are detected to determine a desired steering angle of rear road wheels on a basis of a coefficient related to the vehicle speed and the front wheel steering angle and yawrate. The vehicle speed, however, may not be properly detected when the road wheels tend to be locked in braking operation. If the coefficient is determined by improper detection of the vehicle speed, the rear road wheels will be steered at an unwanted angle.